Generating code coverage report
Code coverage reports become available after you run at least one test with coverage.
Generate the report
From the main menu, select Coverage tool window., or click in the
In the Generate Coverage Report dialog, specify the directory where the generated report will be stored, and optionally select the Open generated HTML in browser checkbox.
Note that if you are going to save a code coverage report for one of the multiple projects opened in the same window, it is important to check the suggested target location, because RubyMine suggests the previously used location.